Schistosomiasis is a snail-borne trematode infection of humans, domestic and wild animals in different parts of Asia, Africa, the Middle East, South America and the Carribbean. Approximately 200 million people in 74 countries are affected; 120 million of these are symptomatic and 20 million have severe disease. Elimination of schistosomiasis has been mainly accomplished by control of the snail host. As measures of snail control, cement-lining of ditches and chemical mollusciciding were most effective in many countries. But the cost of this joint program is too expensive compared with health budget in almost developing countries. Due to persisting conditions of poor health infrastructure, lack of access to clean water and poverty, re-infections in humans still poses a challenge for the long-term control of schistosomiasis. It is hoped that vaccines and better diagnosis of human will help alleviate some of these challenges. However, until these become available, alternative strategies, including blocking parasite transmission in the snail host have been considered. Several studies have been conducted in recent years to begin to understand the molecular basis of the snail-parasite interaction and to identify genes that may be involved in rendering snails resistant to infection.